The present invention relates to a fluidized bed unit and, more particularly, to such a unit including an electrical heater for use during startup.
The use of fluidized beds has been recognized as an attractive means of generating heat. In these arrangements, air is passed through a bed of particulate material, which normally consists of a mixture of inert material and a fossil fuel such as coal, to fluidize the bed and to promote the combustion of the fuel. When the heat produced by the fluidized bed is utilized to convert water to steam, such as in a steam generator, the fluidized bed system offers an attractive combination of high heat release, improved heat transfer to surfaces within the bed, and compact boiler size.
The conventional manner of starting a fluidized bed unit is to employ oil burners, or the like, located in a manner so that they fire above the bed with their flame impinging on the bed surface. However, in this type of arrangement much of the heat is lost to the sidewalls and the fluidizing air which, of course, results in a loss in efficiency and a relatively long bed warm-up time before actual operation can begin.